1. Field of the Invention
The present invention relates in general to scalable image processing, and more specifically to dyadic spatial re-sampling filters for inter-layer texture predictions in scalable video coding.
2. Description of the Related Art
The Advanced Video Coding (AVC) standard, Part 10 of MPEG4 (Motion Picture Experts Group), otherwise known as H.264, includes advanced compression techniques that were developed to enable transmission of video signals at a wide range of bit rates or to enable improved video quality at a given transmission rate. The newer H.264 standard outperforms video compression techniques of prior standards in order to support higher quality video at given bit rates and to enable internet-based video and wireless applications and the like. The standard defines the syntax of the encoded video bit stream along with a method of decoding the bit stream. Scalable Video Coding (SVC) is an extension of the H.264 which addresses coding schemes for reliably delivery of video to diverse clients over heterogeneous networks using available system resources, particularly in scenarios where the downstream client capabilities, system resources, and network conditions are not known in advance, or dynamically changing from time to time.
SVC achieves scalability by using base and enhanced layers concept, where an enhanced layer, or upper layer, is scalable from a lower layer, e.g., a base layer. Whereas H.264 has relatively limited scalability, SVC provides multiple levels of scalability including temporal scalability, spatial scalability, complexity scalability and quality scalability. The base layer should be the simplest form in quality, spatial resolution and temporal resolution. Temporal scalability generally refers to the number of frames per second (fps) of the video stream, such as 7.5 fps, 15 fps, 30 fps, etc. Spatial scalability refers to the resolution of each frame, such as common interface format (CIF) with 352 by 288 pixels per frame, or quarter CIF (QCIF) with 176 by 144 pixels per frame, although other spatial resolutions are contemplated, such as 4CIF, QVGA, VGA, SVGA, D1, HDTV, etc. Up and down sampling, or more generally, re-sampling, of an image signal is a common function performed in image communication systems, including video systems, to facilitate scaling between different spatial resolutions. Dyadic spatial scalability refers to spatial scalability by a factor of two in both horizontal and vertical directions, which is a factor of two for each image or frame. Extended Spatial Scalability (ESS) includes dyadic and non-dyadic spatial re-sampling. Several disadvantages occur when the dyadic case is included in ESS. A first disadvantage is the relatively complex phase calculations associated with ESS. Another disadvantage is the additional low pass filtering for the interpolation of sub-pixels.
It is desired to provide to improve dyadic re-sampling filters for balancing the tradeoff between visual quality, power and memory consumption for image processing.